What are Binding Corporate Rules?
Binding Corporate Rules (BCRs) are internal rules regarding data transfers within multinational companies. BCRs permit a multinational companies to transfer personal data internationally within the same corporate group of companies without violating the GDPR even though the countries to which data is transferred do not otherwise provide an adequate level of data protection.
To be valid, BCRs require numerous provisions and mechanisms to verify compliance including audits and methods for corrective actions.
See GDPR, Article 47
https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:32016R0679&from=EN